Optical component for free-space optical propagation between waveguides

ABSTRACT

An optical component may comprise a horizontal member with two side walls and a substantially transparent end wall protruding from the horizontal member. The end wall, side walls and horizontal member may partially enclose an interior volume, and optical functionality is imparted in any suitable manner on at least a portion of the end wall. An optical assembly may comprise such an optical component mounted on a waveguide substrate along with a planar waveguide and a second waveguide, which are end-coupled by either reflection from the optical component end wall or transmission through the optical component end wall. An end portion of a planar waveguide may be received within the interior volume of the mounted component. Proper positioning of the optical component relative to the waveguides may be facilitated by alignment surfaces and/or alignment marks on the component and/or waveguide substrate.

RELATED APPLICATIONS

This application is a continuation of U.S. non-provisional applicationSer. No. 11/279,250 filed Apr. 11, 2006 (now U.S. Pat. No. 7,142,772),which is a divisional application of U.S. non-provisional applicationSer. No. 10/682,768 filed Oct. 9, 2003 (now U.S. Pat. No. 7,031,575),which in turn claims benefit of U.S. provisional App. No. 60/425,370filed Nov. 12, 2002 and U.S. provisional App. No. 60/466,799 filed Apr.29, 2003. Each of said applications and patents is hereby incorporatedby reference as if fully set forth herein.

BACKGROUND

The field of the present invention relates to optical components. Inparticular, reflective and/or transmissive optical components aredisclosed herein for free-space optical propagation between waveguides.

Planar optical waveguides are suitable for implementing a variety ofoptical devices for use in telecommunications and other fields. Inaddition to the planar waveguides, the planar waveguide substrate oftenalso includes (by fabrication and/or placement thereon):alignment/support structures for placement of optical components/deviceson the substrate; V-grooves and/or other alignment/support structuresfor positioning of optical fibers and/or fiber-optic tapers on thesubstrate; compensators, gratings, filters, and/or other opticalelements/devices; electrical contacts and/or traces for enablingelectronic access to active devices on the substrate; and/or othersuitable components. Reflective and/or transmissive optical elementsincluding, but not limited to, mirrors, beamsplitters, beam combiners,filters, lenses, and so forth are disclosed herein for use with one ormore planar optical waveguides and for free-space optical propagationand/or end-coupling therebetween.

SUMMARY

A method comprises: propagating an optical signal in a first opticalwaveguide positioned on a waveguide substrate; transmitting the opticalsignal out of the first optical waveguide through an end face thereof;receiving into a second optical waveguide positioned on the waveguidesubstrate through an end face thereof at least a portion of the opticalsignal transmitted from the first optical waveguide; and propagating inthe second optical waveguide that portion of the optical signal receivedthrough the end face thereof. The second optical waveguide is opticallyend-coupled with the first optical waveguide. The received portion ofthe optical signal is reflected by or transmitted through an end wall ofan optical component. The optical component comprises (i) a horizontalmember, (ii) two side walls integrally formed with and protruding fromthe horizontal member, (iii) the end wall integrally formed with andprotruding from the horizontal member, the end wall, side walls, andhorizontal member partially enclosing an interior volume, and (iv)optical functionality imparted on at least a portion of the end wall.The two side walls are arranged for engaging the waveguide substrate soas to position the end wall at a desired angle with respect to thewaveguide substrate and so that the waveguide substrate partiallyencloses the interior volume opposite the horizontal member. The opticalcomponent is mounted on the waveguide substrate with the two side wallsengaged therewith.

Objects and advantages of optical components and/or assemblies disclosedherein may become apparent upon referring to the disclosed exemplaryembodiments as illustrated in the drawings and set forth in thefollowing written description and/or claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic top view of a generic optical assembly.

FIG. 2 is a schematic top view of a generic optical assembly.

FIGS. 3A and 3B are schematic top and elevation views, respectively, ofa generic optical assembly.

FIGS. 4A and 4B are schematic top and elevation views, respectively, ofa generic optical assembly.

FIGS. 5A, 5B, 5C, and 5D are top, end, side, and isometric views,respectively, of an exemplary optical component.

FIGS. 6A, 6B, 6C, and 6D are top views of exemplary optical componentsand waveguides.

FIGS. 7A and 7B are schematic top and elevation views, respectively, ofan exemplary optical assembly. FIG. 7C is a schematic elevation view ofan exemplary optical assembly.

FIGS. 8A and 8B are schematic top and elevation views, respectively, ofan exemplary optical assembly. FIG. 8C is a schematic elevation view ofan exemplary optical assembly.

FIG. 9 is a schematic top view of an exemplary optical assembly.

FIG. 10 is a schematic top view of an exemplary optical assembly.

FIGS. 11A and 11B are top views of exemplary dual optical components andwaveguides.

FIGS. 12A. 12B, 12C, 13A, and 13B illustrate exemplary process sequencesfor fabricating optical components.

FIGS. 14A and 14B are schematic isometric views of exemplary opticalcomponents.

FIGS. 15A, 15B, and 15C are plan and cross-sectional views of opticalwaveguides.

FIG. 16 is a schematic top view of an exemplary optical assembly.

It should be noted that the relative proportions of various structuresshown in the Figures may be distorted to more clearly illustrate thepresent invention. Relative dimensions of various optical devices,optical waveguides, optical fibers, optical components, optical modes,alignment/support members, grooves, and so forth may be distorted, bothrelative to each other as well as in their relative transverse and/orlongitudinal proportions. In many of the Figures the transversedimension of an optical element is enlarged relative to the longitudinaldimension for clarity, which will cause variations of transversedimension(s) with longitudinal position to appear exaggerated.

The embodiments shown in the Figures are exemplary, and should not beconstrued as limiting the scope of the present invention as disclosedand/or claimed herein.

DETAILED DESCRIPTION OF EMBODIMENTS

Many of the optical waveguides (including both optical fibers and planarwaveguides) described herein have dimensions and design parameters so asto support only one or a few lowest-order optical modes. At visible andnear-IR wavelengths, the resulting optical modes are typically a few μmup to about 10 or 15 μm in transverse extent. Depending on the nature ofthe waveguide, the guided optical mode(s) may be nearly cylindricallysymmetric, or may differ substantially in transverse extent alongsubstantially orthogonal transverse dimensions. Modes of thesewavelengths and sizes typically exhibit substantially diffractivebehavior beyond the end face of the supporting waveguide, typicallybecoming substantially convergent/divergent sufficiently far from theend face of the supporting waveguide (NA often greater than about 0.1).Accordingly, one or more of the following adaptations may be required toachieve a degree of optical power transfer above an operationallyacceptable level between end-coupled waveguides: maintain the unguidedoptical pathlength between the waveguide end faces as small aspracticable for a particular optical assembly; adapt the end portion ofone or both waveguides for mitigating the diffractive behavior of theoptical mode at the end face of the waveguide; insert one or moreadditional optical elements between the waveguides for refocusing,re-imaging, or otherwise manipulating the mode spatial properties forenhancing end-coupling between the waveguides.

It is often the case in a waveguide-based optical system orwaveguide-based multi-component optical device that opticalfunctionality is to be provided that cannot be readily implementedwithin a waveguide, and must therefore be provided by an opticalcomponent (reflective and/or transmissive) interposed in the opticalpath between end faces of waveguides, with unguided (i.e., free-space)optical propagation between the waveguides (reflected from a reflectiveoptical component and/or transmitted through a transmissive opticalcomponent). In order to implement optical functionality in this waywhile maintaining overall transmission through the optical system at orabove an operationally acceptable level, it is typically necessary toadapt the optical system or multi-component optical device as describedin the preceding paragraph.

FIG. 1 is a schematic diagram of an optical assembly including anoptical component 100 positioned on a planar waveguide substrate 200along with optical waveguides 210, 230, and 250, at least one of whichis a planar waveguide formed on substrate 200. Optical power maypropagate through each of waveguides 210/230/250 in one or more of therespective propagating modes supported thereby. Each waveguide210/230/250 terminates at respective end faces 211/231/251, throughwhich optical power may enter/exit the respective waveguide byend-transfer of optical power (equivalently: end-transfer, end coupling,end-coupled optical power transfer, end-coupled transfer of opticalpower, end-coupled transfer) with respective freely propagating opticalbeams 10/30/50 (freely propagating indicating lack of transverse guidingas provided by a waveguide). Waveguides 210 and 230 and opticalcomponent 100 may be suitably arranged so as to enablereflectively-coupled end-transfer of optical power between waveguides210 and 230 by reflection of optical beams 10 and/or 30 from surfaces102 and/or 104 of optical component 100 (including double-passtransmission through component 100 for reflection from surface 104;reflection only from surface 102 depicted in FIGS. 1, 2, 3A/3B, and4A/4B). Similarly, waveguides 210 and 250 and optical component 100 maybe suitably arranged so as to enable transmissively-coupled end-transferof optical power between waveguides 210 and 250 by transmission ofoptical beams 10 and/or 50 through optical component 100 and surfaces102 and 104 thereof.

Optical component 100 may be adapted in myriad ways for modifying theintensity, spatial characteristics, polarization characteristics, and/orspectral characteristics of optical beams reflected therefrom and/ortransmitted therethrough (i.e., for imparting optical functionality onthe optical component). The generic optical assembly of FIG. 1 maytherefore be employed for implementing a wide array of opticalfunctionality via optical component 100 (which may also serve to enhanceend-coupling between the waveguides) while remaining within the scope ofthe present disclosure and/or the appended claims. Examples of impartingoptical functionality may include, but are not limited to: i) forming atleast one optical coating on at least one surface of the opticalcomponent; ii) providing the optical component with at least one curvedsurface; iii) providing at least one surface of the optical componentwith a spatially-varying surface profile; iv) providing the opticalcomponent with at least one spatially-varying optical property; v)providing the optical component with at least one anisotropic opticalproperty; and/or vi) providing the optical component with at least onespectrally-varying optical property. More specific examples ofadaptations of optical component 100 for imparting optical functionalitymay include (without being limited to): spatial orientation of surfaces102/104; curvature in one or two dimensions of one or both of surfaces102/104; surface discontinuities (such as facet boundaries) on one orboth of surfaces 102/104; reflective, partially reflective, and/oranti-reflective coatings on one or both of surfaces 102/104; diffractivestructures implemented on one or both of surfaces 102/104 and/or withincomponent 100; refractive index spectral and/or spatial discontinuities,gradients, and/or modulations within component 100; birefringent and/ordichroic properties (with respect to linear and/or circularpolarization) within component 100; birefringent and/or dichroiccoatings (with respect to linear and/or circular polarization) on one orboth of surfaces 102/104; Faraday rotation within component 100; opticalabsorption/transmission within component 100; spectral and/or spatialdiscontinuities, gradients, and/or modulations of any one or more of theforegoing. Such adaptations of optical component 100 may be positiondependent or independent, may be wavelength dependent or independent,and may be polarization dependent or independent, as needed forimplementation of particular functionalitie(s) to be provided by theoptical assembly of FIG. 1.

At least one of waveguides 210/230/250 may be implemented as a planarwaveguide formed on substrate 200. If all three waveguides are planarwaveguides formed on substrate 200, spatially-selective materialprocessing techniques may be employed for sufficiently accuratepositioning (within operationally acceptable tolerances) of thewaveguides on the substrate for enabling intended functionality of theoptical assembly. If one or two of waveguides 210/230/250 are not planarwaveguides on substrate 200, substrate 200 may be adapted for suitablymounting such waveguide(s) relative to planar waveguide(s) thereon forenabling (within operationally acceptable tolerances) intendedfunctionality of the optical assembly. For example, one or two ofwaveguides 210/230/250 may comprise an optical fiber (waveguide 250, forexample, as shown schematically in FIG. 2). Substrate 200 may beprovided with corresponding V-groove(s) 201, alignment edge(s) 202,and/or other suitable alignment structure(s) for enabling sufficientlyaccurate passive positioning (as opposed to active positioning, in whichfunctioning of the optical assembly or sub-assembly thereof is monitoredto determine positional accuracy) of the optical fiber(s) relative tothe planar waveguide(s) (within operationally acceptable tolerances). Inanother example, one or two of waveguides 210/230/250 (waveguide 230,for example, as shown schematically in FIGS. 3A/3B) comprises a planarwaveguide formed on a corresponding separate waveguide substrate 239.Substrate 200 and/or substrate 239 may be provided with suitablesupport/alignment structures 203 and 233, respectively, for enablingsufficiently accurate passive positioning (within operationallyacceptable tolerances) of waveguide 230 relative to waveguides 210/250.Alternatively, substrate 200 may be provided with support structure(s)205 and substrates 200 and 239 may be provided with alignment marks 204and 234, respectively, for enabling sufficiently accurate vision-basedpassive positioning (human vision or machine vision; withinoperationally acceptable tolerances) of waveguide 230 relative towaveguides 210/250 (shown schematically in FIG. 4).

Optical component 100 may be adapted for enabling sufficiently accuratepassive positioning (within operationally acceptable tolerances) onsubstrate 200 relative to waveguides 210/230/250 and for in turnenabling intended functionality of the optical assembly. An embodimentof component 100 suitable for placement on substrate 200 near an endface of a planar waveguide (waveguide 250, for example) is shown inFIGS. 5A/5B/5C/5D. Optical component 100 is shown formed on a componentsubstrate that has been spatially-selectively processed to form apartially enclosed pocket or interior volume 106 between side walls 108,a horizontal member 101, and an end wall, the end wall forming opticalcomponent 100. The optical component 100 includes in this exemplaryembodiment substantially flat, substantially vertical inner and outersurfaces 102 and 104, respectively. The other end of the interior volume106 is left open in this example. Horizontal member 101 extends beyondoptical component 100 and side walls 108 in this example, but this neednot be the case.

Use of a substantially homogeneous material for forming component 100results in substantially uniform optical properties within component100, while use of an inhomogeneous material (having one or more spatialdiscontinuities, gradients, and/or modulations) results in similarlyinhomogeneous properties within component 100. Component 100, horizontalmember 101, and side walls 108 may be formed by spatially-selectiveprocessing of the substrate material. Alternatively, an overlayercomprising one or more different materials maybe applied to a substrateand spatially-selectively processed to form component 100 and side walls108; in this case horizontal member 101 may comprise one or both ofsubstrate material and overlayer material(s). Optical component 100 maybe as thin as practicable for maintaining structural integrity withoutrequiring excessive separation between ends of waveguides 210/230/250.Component 100 may typically range between about 10 μm and about 50 μm inthickness, often between about 20 μm and about 30 μm. Thinner opticalcomponents may be employed if fabricated from sufficiently robustmaterial(s) and handled with sufficient care. Thicker optical components100 may be employed (up to 100 μm or more) if necessary or desirable forimplementing particular optical functionality, and/or for laterallyoff-setting reflected beams from the two component surfaces in anoff-normal incidence geometry. One or both of surfaces 102/104 may beprovided with an optical coating for providing optical functionality.Spatially selective material processing may be employed to provide oneor more of: one or more alignment edges and/or vertical and/orhorizontal alignment surfaces on side walls 108 and/or horizontal member101 for engaging corresponding alignment/support structures on waveguidesubstrate 200; one or more alignment marks 124 for enabling vision-basedpositioning of component 100 on correspondingly marked waveguidesubstrate 200; and/or one or more solder pads 123 for securing component100 to substrate 200.

After fabrication, horizontal member 101 with optical component 100thereon is inverted, positioned on substrate 200, and secured theretousing so-called “flip-chip” mounting (as shown in FIGS. 7A/7B and8A/8B). In order to reduce the distance separating the ends ofwaveguides 210/230/250 (thereby somewhat mitigating diffractiveend-coupling losses that may be present) while neverthelessaccommodating optical component 100 and secure mounting/support thereofon substrate 200, at least an end portion of one of the planarwaveguides (waveguide 250 in the illustrated examples) may form a ridgeprotruding from an adjacent area of substrate 200, so that uponflip-chip mounting of optical component 100 on substrate 200, the endportion of waveguide 250 is received within pocket 106 with surface 104of optical component 100 near end face 251 of waveguide 250 (FIGS.6A/6B/6C/6D). Pocket or interior volume 106 may range from about 10 μmin height up to several tens of μm high or more to accommodate typicalplanar waveguides, and may be made any suitable width required toaccommodate a planar waveguide. The width of pocket 106 and/or thepositions/orientations of side walls 108 thereof may be configured topermit placement of optical component 100 at a required angle (withinoperationally acceptable tolerances; as illustrated in the examples ofFIGS. 6A/6B/6C/6D, 7A/7B, and 8A/8B) relative to waveguide 250 (andtherefore also waveguides 210/230). To reduce diffractive losses whilefacilitating mounting of component 100 between the waveguides, thewaveguides may be positioned on the substrate so that upon mounting ofthe optical component 100, each of the waveguide end faces is withinabout 5 μm of a facing component surface 102 or 104. Larger separationsbetween the waveguide end faces and the optical component surfaces mayalso fall within the scope of the present disclosure and/or appendedclaims.

FIG. 6A shows an example of an optical component at substantially normalincidence with respect to component 100, with the end face of thewaveguide also at substantially normal incidence. FIG. 6B shows anon-normal optical component with a substantially normal waveguide endface. End faces of waveguides 210, 230, and/or 250 may be adapted forenabling close positioning of a non-normal optical component 100 withoutexcessive separation between the waveguides. In the examples of FIGS.6C/6D, 7A/7B, and 8A/8B the end faces are angled (i.e., notsubstantially orthogonal to the propagation direction of the respectivewaveguide), thereby allowing a non-normal optical component 100 to bepositioned closer to end faces of each of the waveguides.

In order to reduce unwanted reflective losses at waveguide end faces andat any nominally non-reflective surface of component 100 (when thewaveguide(s) and optical component are of similar refractive index), anindex-matched embedding medium may be interposed between the waveguideend faces and the surfaces of the optical component. This may beaccomplished by embedding the assembled waveguides and optical componentin a substantially index-matched embedding medium, such as a polymer. Asolution or suspension of polymer precursor is applied and flows intospaces between optical surfaces. After curing of the polymer, thewaveguides and optical component and waveguides are embedded. In orderto facilitate flow of the index-matching (or “potting”) medium betweenthe inner surface 104 of the optical component and the end face of thewaveguide received in the pocket of the optical component, one or moreopenings may be provided through one or both side walls 108, aroundcomponent 100 on the end wall, and/or through component substrate 101.Even if waveguide and component materials have substantially differingrefractive indices, an embedding material may still reduce unwantedreflective losses (relative to air or vacuum).

If only transmissively-coupled end-transfer is intended, an opticalcomponent fabricated as disclosed herein may be employed at normal ornear normal incidence (illustrated in FIG. 6A), although non-normalincidence may be employed as well. Optical components for which onlytransmissive optical functionality may be required may include spectralnotch, short-pass, long-pass, and/or bandpass filters, for example,intended to reject one or more incident spectral components that neednot be directed elsewhere. Such functionality may be readily provided byone or more optical coating(s) on one or both of surfaces 102 and 104 ofoptical component 100. Other examples of transmissive-only opticalcomponents may fall within the scope of the present disclosure and/orappended claims. Non-normal incidence with respect to component 100 (asillustrated in FIGS. 6B/6C/6D, 7A/7B, and 8A/8B) typically may berequired for including reflectively-coupled end-transfer. Suchcomponents may include as examples the various spectral filter typesmentioned hereinabove, in which the rejected spectral component(s) mustbe directed to a specific location. Other examples of transmissive plusreflective optical functionality may fall within the scope of thepresent disclosure and/or appended claims.

It may be desirable to suppress at least a portion of unwanted lightreflected, transmitted, and/or scattered by optical component 100. Forexample, a fraction of light emerging from waveguide 230 and reflectedfrom optical component 100 into waveguide 210 may leak through component100. Given the angular misalignment of waveguides 230 and 250, it may beunlikely in many cases that a significant amount of this unwantedtransmitted light would enter waveguide 250. It may nevertheless bedesirable to reduce the amount of such leakage light reaching othercomponents or devices on substrate 200. Side walls 108 may be adaptedfor absorbing such unwanted light (at an operating wavelength forcomponent 100) transmitted through component 100 from waveguide 230, forexample. Alternatively, as shown in FIGS. 7C and 8C, side walls 108 maybe tilted and suitably coated so as to reflect such unwanted transmittedlight downward into the substrate 200, to be absorbed or transmittedaway from components on the substrate surface. These adaptations mayalso serve to suppress unwanted reflection from component 100 of lightemerging from waveguide 250 for transmission through component 100 andinto waveguide 210. Alternatively, an additional waveguide 270 may bepositioned on substrate 200 for receiving unwanted transmitted orreflected optical signals (from waveguides 230 and 250, respectively),as shown in FIG. 16. Such a “beam dump” waveguide may convey unwantedlight away from sensitive components on substrate 200, or may be adaptedin any suitable manner for absorbing or dissipating the unwanted light.It should be noted that the exemplary embodiment of FIG. 16 may also beemployed for implementing a four-port optical assembly, in which any orall of waveguides 210, 230, 250, and/or 270 may be used for transmittingand/or receiving optical signals reflected and/or transmitted bycomponent 100.

Reflectively-coupled end-transfer may be implemented at any suitableangle of incidence on optical component 100. Many optical coatingsand/or components exhibit properties which vary with angle of incidence,and which may have wavelength and/or polarization dependencies that inturn depend on angle of incidence (further complicated by the range ofincident angles present in a convergent or divergent incident beam).These dependencies are typically at a minimum near normal incidence andincrease with increasing angle of incidence, which may in some instancesimpose an upper limit on the angle of incidence that may be used for agiven optical component 100. A lower limit for a usable angle ofincidence may be determined in part by the degree of diffractive lossesthat may be tolerated in the optical assembly. In FIGS. 7A and 8A,waveguides 210 and 230 are shown merging as they approach component 100.Parasitic optical losses increase with increasing length of the mergedportion of the waveguides, which in turn increases with decreasing angleof incidence (and therefore a decreased angle of separation between thewaveguides). In any given assembly the optical performance required(which may be degraded by a larger angle of incidence) may be balancedagainst optical loss induced by the merged section of the waveguides(typically worsened by a smaller angle of incidence). Geometric andspace constraints on the waveguide substrate may also come into play. Arange of compromise values is typically available for a particularoptical assembly incorporating particular optical functionality via theoptical component 100. Many optical assemblies may have an incidenceangle below about 45° (i.e., reflectively coupled waveguides forming anangle less than about 90°), often between about 7° and about 18° (i.e.,reflectively coupled waveguides forming an angle between about 15° andabout 35°). However, any suitable angle of incidence on opticalcomponent 100 (and corresponding angle between reflectively coupledwaveguide) shall fall within the scope of the present disclosure and/orappended claims.

A waveguide having a thin core (i.e., less than about 3 μm high, oftenless than about 1 μm high) may be employed for reducing optical lossesat small incidence angles on optical component 100, as shown in FIGS.15A-15C. The presence of one of the cores 212 and 232 gives rise toparasitic optical loss in the other, and this parasitic loss is roughlyproportional to the cross-sectional area of the interfering core. Forgiven optical mode sizes supported by waveguides 210 and 230, reducingthe cross-sectional area of the respective cores 212 and 232correspondingly reduces the level of parasitic optical loss from onecore induced by the other. For a given angle between the waveguides, useof thin waveguide cores (as shown in the cross-section of FIG. 15C)reduces parasitic optical losses relative to thicker waveguide cores (asshown in the cross-section of FIG. 15B). For example, for waveguidesseparated by 20°, cores of about 6-7 μm in height and width may exhibitoptical loss of about 0.8 dB or more. In contrast, for the same angularseparation, thin cores about 0.5 μm high by about 5 μm wide may exhibitonly about a 0.2 dB optical loss. In addition, more complete and moreuniform filling of the acute angle between the cores with claddingmaterial may further reduce optical losses for thin cores relative tothicker cores (without the need for high temperatures or additionalprocessing steps for achieving re-flow of cladding material).

An example of multiple functionalities provided by optical component 100is shown in FIG. 9. In this example, component 100 may act as a spectralfilter for directing a first spectral component (near λ₁) of an incidentoptical signal (incident optical beam 10) from planar waveguide 210 toplanar waveguide 230 (reflected optical beam 30), and transmitting asecond spectral component (near λ₂) of the incident optical signal fromplanar waveguide 210 to planar waveguide 250 (transmitted optical beam50). Surface 102 may be provided with a suitable spectrally-selectivereflective coating for substantially reflecting the first spectralcomponent (near λ₁) while substantially transmitting the second spectralcomponent (near λ₂), thereby providing the spectral filterfunctionality. Surface 104 may be provided with a suitableanti-reflective coating (near λ₂) if necessary or desirable. Inaddition, surfaces 102 and/or 104 may be provided with curvature (in oneor both dimensions; only shown in the horizontal dimension in FIG. 9)for improving end-coupling between waveguides 210 and 230 and/or betweenwaveguides 210 and 250. In the exemplary embodiment of FIG. 9, surface102 is shown as a concave surface. The curvature of surface 102 may bedesigned to act as a focusing mirror, receiving incident optical beam 10and producing reflected optical beam 30 with reduced divergence or adegree of convergence, thereby improving end-coupling between waveguides210 and 230. Curved surface 102 may be designed to substantially modematch waveguides 210 and 230. The curvature of surface 104 may bedesigned so that component 100, with curved surfaces 102 and 104, actsas a focusing lens (a meniscus lens in this example), receiving incidentoptical beam 10 and producing transmitted optical beam 50 with reduceddivergence or a degree of convergence, thereby improving end-couplingbetween waveguides 210 and 250. Curved surfaces 102 and/or 104 may bedesigned to substantially mode match waveguides 210 and 250. In additionto curved surfaces 102 and/or 104, component 100 may includeindex-gradient material for providing focusing of transmitted opticalbeam 50. If the reflected beam 30 is reflected from surface 104 insteadof surface 102, both curved surfaces as well as any index gradientpresent will influence mode matching between waveguides 210 and 230.

Many other examples of specific optical functionalities, alone or invarious combinations, may be provided by an optical component 100 thatfall within the scope of the present disclosure and/or appended claims.Such functionalities may be provided by suitable adaptation of component100 and/or one or both of surfaces 102 and 104 thereof. Examples of suchfunctionalities may include, but are not limited to: spectral filtering,spectral separation, spectral dispersion (spatial and/or temporal),spectral manipulation (amplitude and/or phase), spatial manipulation(amplitude and/or phase), attenuation, focusing, de-focusing,collimating, mode matching, polarization selection (linear and/orcircular), polarization retardation (linear and/or circular),polarization manipulation, optical isolation, aperturing, vignetting,beam splitting, beam combining, multiplexing, de-multiplexing,bi-directional receiving/transmitting, and so forth.

Exemplary optical assemblies are shown in FIGS. 10A and 10B, eacharranged for functioning as a bi-directional optical transceiver. Planarwaveguides 410/430/450/460/470 are provided on transceiver substrate400. Two incoming wavelength-multiplexed optical signals (centered nearλ₁ and λ₂, respectively) enter the bi-directional transceiver from anoptical fiber 490 end-coupled to waveguide 410. Optical fiber 490 isreceived in V-groove 491 on substrate 400 for positioning the opticalfiber relative to waveguide 410. Waveguide 410 and optical fiber 490 maybe adapted for optical power transfer therebetween in any suitablemanner, including transverse-transfer (as taught in U.S. PatentApplication Pub. No. 2003/0081902) and end-transfer. It is typically thecase that the incoming optical signals arrive at the end of opticalfiber 490 in an unknown and varying polarization state. A modulatedlaser source 480 (optical output centered near at λ₃) is shown coupledto waveguide 470. Output of laser source 480 may be transferred intowaveguide 470 in any suitable manner, including end-transfer ortransverse-transfer. Support/alignment structures and/or alignmentmarkings (not shown in FIGS. 10A and 10B) may be provided on lasersource 480 and substrate 400 for positioning and securing laser source480 on substrate 400 relative to waveguide 470.

A first spectral filter 412 as described hereinabove is positionedbetween waveguides 410 and 450. In FIG. 10A, filter 412, may be designedto substantially reflect the first incoming optical signal (λ₁) whilesubstantially transmitting the second incoming optical signal (λ₂) andthe laser output signal (λ₃). Waveguide 430 may be positioned to receivethe reflected first incoming optical signal and convey it to aphotodetector 436 for conversion into a first electrical output signal.Second and third spectral filters 432 and 434 may be provided withingaps in waveguide 430 for reflecting the second incoming optical signal(λ₂) while substantially transmitting the first incoming optical signal(λ₁), thereby substantially isolating photodetector 436 from undesiredreflection of the second incoming optical signal (λ₂) from spectralfilter 412. Any photodetector having suitable performancecharacteristics (bandwidth, wavelength response, and so forth) may beemployed. A fourth spectral filter 452 is provided between waveguides450 and 470, and may be designed to substantially reflect the secondincoming optical signal (λ₂) while substantially transmitting the laseroutput signal (λ₃). Waveguide 460 may be positioned to receive thereflected second incoming optical signal and convey it to aphotodetector 466 for conversion into a second electrical output signal.Additional spectral filters may be provided along waveguide 460, ifneeded or desired, for substantially isolating photodetector 466 fromother optical signals (λ₁ and/or λ₃). Any photodetector having suitableperformance characteristics (bandwidth, wavelength response, and so on)may be employed. Laser output is transmitted along waveguide 470,through spectral filter 452, along waveguide 450, through spectralfilter 412, along waveguide 410, and into optical fiber 490. In someinstances undesirable reflection of the output optical signal fromspectral filters 412 and 452 may be of little consequence (other thanoverall attenuation of the output signal), since the reflections are notin a direction that affects other components or devices on thetransceiver. Filters 412 and 452 may be adapted, if needed or desired,for absorbing or redirecting unwanted reflection of the output opticalsignal (as described hereinabove), or additional waveguide(s) may beprovided on substrate 400 for receiving such unwanted reflected light(as described hereinabove).

In FIG. 10B, filter 412, may be designed to substantially transmit thefirst incoming optical signal (λ₁) while substantially reflecting thesecond incoming optical signal (λ₂) and the laser output signal (λ₃).Waveguide 450 may be positioned to receive the transmitted firstincoming optical signal and convey it to a photodetector 436 forconversion into a first electrical output signal. Second and thirdspectral filters 452 and 454 may be provided within gaps in waveguide450 for reflecting the second incoming optical signal (λ₂) and perhapsalso the output optical signal (λ₃), while substantially transmittingthe first incoming optical signal (λ₁), thereby substantially isolatingphotodetector 436 from any undesired transmission of other opticalsignals (λ₂ and/or λ₃) through spectral filter 412. Any photodetectorhaving suitable performance characteristics (bandwidth, wavelengthresponse, and so forth) may be employed. A fourth spectral filter 432 isprovided between waveguides 430 and 460, and may be designed tosubstantially transmit the second incoming optical signal (λ₂) whilesubstantially reflecting the laser output signal (λ₃). Waveguide 460conveys the second incoming optical signal (λ₂) to a photodetector 466for conversion into a second electrical output signal. Additionalspectral filters may be provided along waveguide 460, if needed ordesired, for substantially isolating photodetector 466 from otheroptical signals (λ₁ and/or λ₃). Any photodetector having suitableperformance characteristics (bandwidth, wavelength response, and so on)may be employed. Laser output signal (λ₃) is transmitted along waveguide470, reflected from spectral filter 432, transmitted along waveguide430, reflected from spectral filter 412, transmitted along waveguide 410and into optical fiber 410. Filters 412 and 432 may be adapted, ifneeded or desired, for absorbing or redirecting unwanted transmission ofthe output optical signal (as described hereinabove), or additionalwaveguide(s) may be provided on substrate 400 for receiving suchunwanted transmitted light (as described hereinabove).

Which of the configurations of FIGS. 10A and 10B, or variants thereof,is employed may depend on a variety of factors, such as the levelisolation required for the laser and/or photodetectors, low incomingsignal levels, detection efficiency, laser output power, device sizeconstraints, and so forth. These embodiments are only two of manyexamples of multi-component optical devices that may be implementedusing planar waveguides and optical components within the scope of thepresent disclosure and/or appended claims.

The spectral reflectance/transmittance characteristics of the coatingsemployed for spectral filters 412/432/434/452/454 typically vary withangle of incidence, and typically differ for S and P incidentpolarizations as the angle of incidence increases from 0° (i.e., normalincidence). The incoming optical signals typically arrive throughoptical fiber 490 in well-defined but unknown polarization states, andthese polarization states may vary in unknown ways with time (theincoming signals perhaps traversing differing paths through an opticaltelecommunications system at differing times). The effect of thispolarization variability of the performance of spectral filters412/432/434/452/454 may be maintained at or below an operationallyacceptable level by selecting a sufficiently small angle of incidence.“Sufficiently small” typically depends on the specific performancerequirements for a specific device. For example, widely separatedwavelengths λ₁, λ₂, and λ₃ may allow a wider range of angle of incidencethan more closely spaced wavelengths. The geometric arrangement of thewaveguides and spectral filters typically imposes a minimum angle ofincidence. In the exemplary embodiment, spectral filters 432/434 (FIG.10A) or 452/454 (FIG. 10B) may be arranged near normal incidence(thereby substantially reducing polarization-dependent performance),since it need only reject the reflected wavelength. Spectral filters412/452 (FIG. 10A) or 412/432 (FIG. 10B) typically require off-normalincidence, since the reflected wavelength must be directed to anotherwaveguide. The angles of incidence for these off-normal spectral filtersare typically selected to be small enough to maintainpolarization-dependent performance variations within operationallyacceptable limits, and large enough to accommodate suitable geometry ofthe waveguides. An angle of incidence of about 10° is shown in theexemplary embodiment (about 20° between reflectively coupledwaveguides); angles between reflectively coupled waveguides in thesetypes of bi-directional assemblies may typically range between about 15°and about 35°. Specific upper and lower limits for the angle ofincidence may typically vary depending on the detailed performancespecifications of a specific device (in some instances falling outsidethe exemplary range given above), while remaining within the scope ofthe present disclosure and/or appended claims.

As shown in the exemplary embodiment of FIGS. 10A and 10B, spectralfilters 432 and 434 are formed on a common component substrate. A pocketor interior volume is formed as described hereinabove partially enclosedbetween two side walls, two end walls, and the horizontal member. Eachend wall may serve as a transmissive/reflective optical component asdescribed herein, and the pocket may accommodate a waveguide segmenttherein. The enclosed waveguide segment may therefore be transmissivelycoupled at each end through the end walls to two other waveguidesoutside the pocket. Such a two-component substrate (components 100 a and100 b on horizontal member 101) and the waveguide segment 310 enclosedtherein may be adapted for normal or non-normal incidence, as needed ordesired (FIGS. 11A/11B). If an embedding medium is to be employedbetween the ends of waveguide 310 and the inner surfaces of components100 a and 100 b, one or more openings may be provided through one orboth side walls, through one or both end walls around the opticalcomponent(s), and/or through horizontal member 101. Such openings permitthe embedding medium to flow into interior volume 106 and fill spacesbetween the optical surfaces.

A variety of materials and fabrication techniques may be employed forforming optical component 100, interior volume 106, side walls 108, andother structures on horizontal member 101. Depending on the intendedwavelength range for use of optical component 100, different materialsmay be employed. Suitable materials may include, but are not limited to,semiconductors (including but not limited to silicon, GaAs, InP, otherIII-V semiconductors, and/or semiconductor alloys and/or oxides),crystalline materials, silica or silica-based materials, other glasses,polymers, and myriad other examples not explicitly set forth herein butthat may nevertheless fall within the scope of the present disclosureand/or appended claims. A single material may be employed for bothhorizontal member 101 and optical component 100, or one material may beemployed for horizontal member 101 and another material overlayerthereon used for forming optical component 100.

Spatially-selective processing may be used on a wafer scale forconcurrent fabrication of multiple optical components on a common wafer.The optical component 100 protrudes from the horizontal member, andsurfaces 102 and/or 104 may be substantially perpendicular to thesurface of a substantially planar wafer (FIGS. 12A/12B/12C;non-perpendicular surfaces may be acceptable or desirable in someinstances). Horizontal member 101 and any horizontal support/alignmentsurfaces are defined by the planar substrate wafer, while substantiallyvertical alignment and/or optical surfaces are defined by spatiallyselective processing steps. The quality of surfaces 102/104 isdetermined by the nature of the spatially-selective steps used to formthem. Varying degrees of surface quality may be attained depending onthe specific techniques used and the precise manner in which they arecarried out. Some exemplary processing techniques for forming surface102/104 may include, without being limited to, dry etch processes (suchas reactive ion etching), anisotropic wet etch processes (restricted tospecific crystallographically defined surfaces), cleaving (alongcrystallographically defined cleavage planes; may only be applicable forsurface 102 since the substrate wafer is cleaved along with component100), and/or cutting with a precision saw or other mechanical cuttingimplement.

Optical coatings applied to these “vertical” surfaces 102 and/or 104 maybe applied on a wafer scale in some instances (FIGS. 12A and 12B).So-called conformal deposition techniques may be used to coat bothhorizontal and vertical surfaces with layers of substantially uniformthickness, for example. In FIG. 12A, coatings are provided in this wayfor both surfaces 102 and 104 (same or differing coatings for the twosurfaces), after which the wafer is divided into individual components.A wider array of coatings and coating techniques may be brought to bearon vertical surfaces 102/104 if a wafer-scale substrate is first cutinto strips, or “bars”, each having thereon a single row of multiplecomponents (FIGS. 12B and 12C). In FIG. 12B, a conformal coating isapplied on a wafer scale to surfaces 104 before division of the waferinto bars. After division into bars, the bars may be flipped about 90°so that surfaces 102 are “horizontal” with respect to a coating chamberor other material deposition apparatus. The bars may be divided intoindividual components after depositing a desired coating on surfaces 102of the bars. In FIG. 12C, the wafer is divided into bars before anycoatings are deposited. After division into bars, the bars may beflipped about 90° and a desired coating may be applied to one ofsurfaces 102 or 104. The bars may then be flipped about 180° and adesired coating (same coating or a different coating) may be applied tothe other of surfaces 102 or 104. After application of the coating(s),the bars may be divided into individual components.

Exemplary embodiments shown in FIGS. 5A/5B/5C/5D and 6A/6B/6C/6D mayhave optical component 100, side walls 108, and horizontal member 101formed from a single substantially homogeneous substrate material.Suitable substrate materials may include silicon, InP and/or other III-Vsemiconductors, other suitable semiconductors, semiconductor oxidesand/or alloys, and/or other suitable materials. Alternatively, component100 and side walls 108 may be formed from an overlayer 90 on a substrate91 (as in FIGS. 12A/12B/12C), for example a silica or silica-basedoverlayer on a silicon substrate (other overlayer/substrate combinationsmay be employed). The overlayer 90 may comprise a single substantiallyhomogeneous layer, resulting in a substantially homogeneous component100, or may comprise a multiple layers of differing materials, resultingin a vertical discontinuity, gradient, or modulation of the opticalproperties of component 100. Exemplary process diagrams are shown inFIGS. 12A/12B/12C. Spatially-selective etching of layer 90 or substrate91 (if no overlayer is present) may be employed for forming pocket 106,inner surfaces of sidewalls 108, and surface 104 of optical component100. Additional alignment/support structures (if present; none shown inFIGS. 5A/5B/5C/5D and 6A/6B/6C/6D) and/or alignment marks 124 may beprovided as well (concurrently or sequentially with pocket 106), inaddition to other elements such as solder pads and the like, if desired.Surface 102 may also be formed by spatially-elective etching(concurrently or sequentially with forming pocket 106 and/or supportstructures and/or alignment marks 124), or surface 102 may be providedby a precision saw cut followed by a re-flow or annealing step or someother suitable smoothing step (a wet etch step, for example), or surface102 may be formed by precision cleaving of the wafer (including bothcomponent 100 and horizontal member 101) into bars 92. Thespatially-selective etch steps employed and/or the saw cut may becarried out in a manner to provide substantially flat, substantiallyvertical surfaces 102/104 (within operationally acceptable tolerances).Etching or cleaving restricted to semiconductor crystal planes producessurfaces oriented to the accuracy enabled by orientation of thesubstrate wafer.

Depending on the nature of the optical component to be formed, it may bedesirable for surfaces 102/104 to be substantially parallel, or for adesigned wedge angle to be provided between them, in either case withinoperationally acceptable tolerances. Such a wedge angle may be providedby the horizontal dimension by suitable spatial control of etch, cleave,and/or saw cut processing step(s). A wedge angle in the verticaldimension may be achieved by adaptation of etch, cleave, and/or saw cutprocessing step(s) to form the desired wedge angle. While etching hasbeen set forth in the preceding fabrication example, it should be notedthat other spatially-selective material removal techniques,spatially-selective material deposition techniques, or a combination ofspatially-selective material deposition and removal techniques, may bealso be employed for forming optical component 100. Any desiredhorizontal variation in the optical properties of component 100(transverse or longitudinal) may be provided at this point by suitablespatially-selective processing of the end wall of interior volume 106.

Once surfaces 102 and 104 have been formed, thereby forming a “blank”for optical component 100, coatings may be applied to one or both ofsurfaces 102/104 as described hereinabove. These coatings may be of anysuitable type for providing the 11 desired functionality, and may beprovided by any suitable method for providing such coatings. Forexample, optical component 100 may comprise a dichroic beamsplitter orbeam combiner (i.e., substantially reflective at one or more designwavelengths or wavelength bands, substantially transmissive at one ormore other design wavelengths or wavelength bands; may also be referredto as a spectral filter). The spectral and polarization characteristicsof transmission and reflection required may vary widely and may bedetermined by: the intended use of the component 100 and specificationstherefor, design and manufacturing capabilities for providing thecoating(s), separation of the design wavelengths or wavelength bands,angle of incidence and polarization characteristics of incident opticalsignals, and other relevant parameters, while remaining within the scopeof the present disclosure and/or the appended claims. Such a filtercoating may be applied to either of surfaces 102 and 104. If necessaryor desirable, additional reflection from the other surface may besuppressed by providing a suitable anti-reflective coating thereon.Unwanted reflection may be redirected by providing a wedge angle betweenthe surfaces 102 and 104, or may be laterally displaced by providingcomponent 100 with sufficient thickness in an off-normal incidencegeometry (for example, a component about 100 μm thick at about a 10° to15° incidence angle sufficiently may typically suppress back-coupling ofan unwanted reflection into the waveguide). If component 100 and thewaveguide have similar indices (around 1.4-1.5 for silica-basedwaveguides and components, for example), embedding the component and theend faces of the waveguide with an index-matching medium may obviate theneed for an anti-reflection coating, a wedge angle, and/or a thickoff-setting component. If component 100 and the waveguides differsubstantially in refractive index (1.4-1.5 for silica-based waveguidesand 2.9-3.4 for semiconductor-based components, for example), then oneor more of an anti-reflection coating, a wedge angle, and/or a thickcomponent may be required to sufficiently suppress unwanted reflectionfrom the component 100, whether or not an embedding medium is employed.

As noted hereinabove, coatings may be provided on surface(s) 102/104during wafer-scale processing using conformal deposition techniques, orthe wafer may be divided into bars with single rows of components andcoated using a wider array of coating techniques. Some embodiments of anoptical components shown herein include a pocket 106 with non-parallelside walls 108 (i.e., pocket 106 narrows from the open end toward theoptical component). This has been described as enabling positioning ofthe optical component at a desired angle of incidence relative to awaveguide within pocket 106. The widening of the pocket may alsofacilitate application of an optical coating to the inner surface 104 ofthe optical component 100. It should also be noted that fordual-component substrates (as in FIGS. 11A/11B), any coating(s) appliedto the inner surface of one or both components 100 a/100 b are mostreadily applied during wafer-scale processing. Dividing the wafer intobars in this instance does not provided improved access to the innersurface(s) of the component(s) for applying a coating.

The spatially-selective processing steps of FIGS. 12A/12B/12C forfabricating optical component 100 substantially perpendicular to a wafermay be implemented on a wafer scale for concurrent fabrication of manycomponents on a common wafer (dozens, hundreds, or thousands ofcomponents per wafer). In this way significant economies of scale may berealized. As already pointed out, some manufacturing steps may not besuitable for implementation on a wafer scale, but may still be performedsimultaneously for multiple devices without manipulation of individualcomponents. For example, some process sequences for providing an opticalcoating on surface 102 or 104 (substantially orthogonal to the wafersurface) might be complex to perform on a wafer scale, particularly ifthe desired coating comprises multiple coating layers. The surfacesmight be more readily coated, or more complex, precision multi-layercoatings more readily applied, if the surface to be coated is orientedso that it is substantially orthogonal to a deposition direction of acoating apparatus. Initial cleavage or division of the wafer (aftercompletion of wafer-scale processing steps) in one dimension yields barsor strips of the wafer each with a single row of components thereon. Theinitial division may be done so that the surfaces to be coated aresubstantially parallel to the long axis of the bar. The optical coatingsmay then be applied to surfaces 102 and/or 104 as required, concurrentlyfor multiple components on each bar, without handling individualcomponents. It may be possible to coat multiple bars concurrently in acommon coating apparatus. Once the coating(s) have been applied, thebars may be further divided to yield individual components.

A variety of techniques may be employed during process sequences (suchas in FIGS. 12A/12B/12C) for providing more general opticalfunctionalities for component 100, as described hereinabove.Multi-layer, gradient, or modulated materials of a wide variety of types(super-lattice materials, quantum well materials, doped materials, indexgradient materials, and so on) may be used to provide verticaldiscontinuities, gradients, and/or modulations of opticalcharacteristics of component 100. Such materials may be formed as asubstantially uniform set of layers, with spatially-selective etching orother material spatially-selective removal of material employed to formoptical component 100. A sequence of spatially-selective depositions ofdiffering materials may be employed to form optical component 100. Ineither case, wafer-scale processing may be employed for concurrentfabrication of many components. Spatially-selective material processingmay be employed for providing horizontal discontinuities, gradients,and/or modulations of optical properties of component 100, and may beimplemented on a wafer scale for many components concurrently. Spatialdiscontinuities, gradients, and/or modulations of coatings applied tosurfaces 102 and/or 104 (including surface gratings) may be providedusing any suitable spatially selective coating and/or processingtechniques, which may be implemented for multiple componentsconcurrently on a common bar. Control of the horizontal orientation ofsurfaces 102/104 by spatial control of processing steps was describedhereinabove. In a similar manner, spatial control of processing stepsmay be employed for providing a curvilinear and/or faceted horizontalprofile for one or both of surfaces 102/104. Such surface profiles maybe provided in the vertical dimension as well by suitable modificationof spatially selective processing. For example, multi-step and/orgray-scale lithography might be employed for providing such verticalsurface profiles. Any one or more of these and any other suitableprocessing steps and/or adaptations thereof may be employed forproviding optical component 100 with intended optical functionalitywhile remaining within the scope of the present disclosure and/orappended claims.

Wafer-scale spatially-selective processing may be used for concurrentfabrication of multiple optical components on a common wafer, in whicheach optical component 100 and surfaces 102/104 thereof aresubstantially parallel to a substantially planar wafer surface (FIGS.13A/13B; the “vertical” optical component end wall now lies parallel tothe substrate wafer). Such an arrangement during spatially-selectiveprocessing may result in improved optical quality of these surfaces, andmay enable wafer-scale application of optical coatings on surface 102and/or 104 of any desired precision and/or complexity. In exemplaryprocess sequences (FIGS. 13A/13B), a substantially planar silicon wafer500 is first provided with a substantially uniform overlayer 502 thatwill eventually form the end wall of interior volume 106 (and opticalcomponent 100). Overlayer 502 may comprise silica, silicon nitride, orsilicon oxynitride on silicon wafer 500, for example. InP or othersuitable III-V semiconductor or alloy may be equivalently employed assubstrate 500, with InP or other III-V or alloy or oxide thereof may beemployed as overlayer 502. Other substantially homogeneous overlayersmay be employed on any suitable wafer material while remaining withinthe scope of the present disclosure and/or appended claims. Overlayer502 may instead comprise a multi-layer material for providing opticalfunctionality (with material variation along the eventual opticalpropagation direction within component 100). The overlayer may bepatterned and etched, leaving optical component layers 504 that willeach eventually serve as the end wall of a pocket 106, surrounded byexposed regions of wafer 500. If transverse variation in the opticalproperties of optical component 100 is desired, suitablespatially-selective processing of areas 504 may be employed to providethe same. If surface 102 is to be curved, the curved surface may beprovided at this point using gray-scale lithography or other similartechniques to alter the surface profiles of areas 504 (in one or bothdimensions).

Wafer 500 may then be processed to form passages 506 therethroughadjacent to component layers 504. Wafer 500 is then flipped over andprocessed from the other side to remove substrate material from behind acentral portions of component layers 504. A material-specific etch isemployed to completely remove wafer material from the central portion ofthe back side of area 504 (which becomes surface 104 of opticalcomponent 100), while leaving a suitably high-optical-quality surface onthe back side of component layers 504. An annealing or smoothing processmay be employed if needed or desired. If a curved surface 104 isdesired, it may be provided at this point using gray-scale lithographyor other similar techniques to alter the back-side surface profiles ofcomponent layers 504 (in one or both dimensions). The generally verticalsubstrate side walls formed during this step form the inner surfaces ofhorizontal member 101 and side walls 108 in the finished opticalcomponent. Depending on the etch process used and the designed geometry,the substrate side walls may be substantially vertical (yieldingsubstantially parallel side walls 108) or may be angled (yielding aninterior volume 106 with a wide open end and narrowing toward opticalcomponent 100, as shown hereinabove). Any desired optical coating may beapplied on a wafer scale to the back surface of the wafer 500, therebyproviding an optical coating for surfaces 104 of many opticalcomponents.

Wafer 500 may be flipped once more, and any desired optical coatingapplied on a wafer scale to the front surface of the wafer, includingcomponent layers 504 (eventually surfaces 102 of optical components100). The component layer areas 504 of the overlayer thus forms the“blank” for optical component 100, and the coatings applied on a waferscale to the front and back surfaces of the wafer serve as the opticalcoatings for surfaces 102 and/or 104. Once the wafer-scale processing iscomplete, the wafer may be cut into individual optical components (FIG.13A). Precision saw cuts may be employed, for example, to divide wafer500 into individual optical components, or other precision cutting orcleaving procedure(s) may be employed. The surfaces produced by dividingthe wafer form the outer and bottom surfaces (upon flip-chip mounting)of side walls 108 in the finished optical components (FIGS. 14A/14B).The precision position and orientations of these surfaces is determinedby the precision of the wafer-dividing procedures used. The outer and/orbottom surfaces of the side walls 108 may serve to accurately positionoptical component 100 on substrate 200 upon assembly with waveguide210/230/250 (as in FIGS. 7A/7B and 8A/8B). It should be pointed out thatthe resulting horizontal member 101 that results from this processingsequence is substantially perpendicular to the wafer before separationinto individual components. In order to provide alignment and/orassembly structures on the bottom surface of side walls 108 (such assolder pads 123, alignment markings 124, alignment edges, and so forth),the wafer may be divided into bars, the bars flipped about 90°, and thedesired structures formed on the bottom surface of the side walls (FIG.13B). Once processing of the bottom of the side walls is complete, thebars may be divided into individual components.

In the foregoing exemplary embodiments of an optical assembly, as wellas other similarly implemented embodiments, spatially-selective materialprocessing techniques may be employed for achieving sufficientlyaccurate relative positioning (within operationally acceptable limits)of elements provided on substrate 200, such as any of waveguides210/230/250 that are implemented as planar waveguides on substrate 200,V-groove(s) 201, alignment edge(s) 202, alignment/support structure(s)203/205/223, and/or alignment mark(s) 204/224. Similarly,spatially-selective material processing techniques may be employed forachieving sufficiently accurate relative positioning (withinoperationally acceptable limits) of elements provided on a separatesubstrate 239, such as waveguide 230, alignment/support structures 233,and/or alignment marks 234. These spatially-selective processing stepsfor fabricating substrate 200 (and structures thereon) may beimplemented on a wafer scale for concurrent fabrication of manysubstrates on a common wafer (dozens, hundreds, or thousands ofsubstrates per wafer). In this way significant economies of scale may berealized. After division of the wafer into individual substrates 200,any required optical component(s) 100, separate waveguide(s),photodetector(s), optical fiber(s), and so forth may be positioned andsecured thereon to provide a functional optical assembly. Variousgrooves, alignment edges, alignment/support structures, alignmentmarkings, and so forth readily enable sufficiently accurate passiveassembly (within operationally acceptable tolerances) for implementingintended optical functionalitie(s) of the optical assembly.

For purposes of the foregoing written description and/or the appendedclaims, the term “optical waveguide” (or equivalently, “waveguide”) asemployed herein shall denote a structure adapted for supporting one ormore optical modes. Such waveguides shall typically provide confinementof a supported optical mode in two transverse dimensions while allowingpropagation along a longitudinal dimension. The transverse andlongitudinal dimensions/directions shall be defined locally for a curvedwaveguide; the absolute orientations of the transverse and longitudinaldimensions may therefore vary along the length of a curvilinearwaveguide, for example. Examples of optical waveguides may include,without being limited to, various types of optical fiber and varioustypes of planar waveguides. The term “planar optical waveguide” (orequivalently, “planar waveguide”) as employed herein shall denote anyoptical waveguide that is formed on a substantially planar substrate.The longitudinal dimension (i.e., the propagation dimension) shall beconsidered substantially parallel to the substrate. A transversedimension substantially parallel to the substrate may be referred to asa lateral or horizontal dimension, while a transverse dimensionsubstantially perpendicular to the substrate may be referred to as avertical dimension. Examples of such waveguides include ridgewaveguides, buried waveguides, semiconductor waveguides, otherhigh-index waveguides (“high-index” being above about 2.5), silica-basedwaveguides, polymer waveguides, other low-index waveguides (“low-index”being below about 2.5), core/clad type waveguides, multi-layer reflector(MLR) waveguides, metal-clad waveguides, air-guided waveguides,vacuum-guided waveguides, photonic crystal-based or photonicbandgap-based waveguides, waveguides incorporating electro-optic (EO)and/or electro-absorptive (EA) materials, waveguides incorporatingnon-linear-optical (NLO) materials, and myriad other examples notexplicitly set forth herein which may nevertheless fall within the scopeof the present disclosure and/or appended claims. Many suitablesubstrate materials may be employed, including semiconductor,crystalline, silica or silica-based, other glasses, ceramic, metal, andmyriad other examples not explicitly set forth herein which maynevertheless fall within the scope of the present disclosure and/orappended claims.

One exemplary type of planar optical waveguide that may be suitable foruse with optical components disclosed herein is a so-called PLCwaveguide (Planar Lightwave Circuit). Such waveguides typically comprisesilica or silica-based waveguides (often ridge or buried waveguides;other waveguide configuration may also be employed) supported on asubstantially planar silicon substrate (often with an interposed silicaor silica-based optical buffer layer). Sets of one or more suchwaveguides may be referred to as planar waveguide circuits, opticalintegrated circuits, or opto-electronic integrated circuits. A PLCsubstrate with one or more PLC waveguides may be readily adapted formounting one or more optical sources, lasers, modulators, and/or otheroptical devices adapted for end-transfer of optical power with 11 asuitably adapted PLC waveguide. A PLC substrate with one or more PLCwaveguides may be readily adapted (according to the teachings of U.S.Patent Application Pub. No. 2003/0081902 and/or U.S. App. No.60/466,799) for mounting one or more optical sources, lasers,modulators, photodetectors, and/or other optical devices adapted fortransverse-transfer of optical power with a suitably adapted PLCwaveguide (mode-interference-coupled, or substantially adiabatic,transverse-transfer; also referred to as transverse-coupling).Reflective and/or transmissive optical components as disclosed hereinmay be readily employed with one or more suitably adapted PLCwaveguides.

For purposes of the foregoing written description and/or appendedclaims, “spatially-selective material processing techniques” shallencompass epitaxy, layer growth, lithography, photolithography,evaporative deposition, sputtering, vapor deposition, chemical vapordeposition, beam deposition, beam-assisted deposition, ion beamdeposition, ion-beam-assisted deposition, plasma-assisted deposition,wet etching, dry etching, ion etching (including reactive ion etching),ion milling, laser machining, spin deposition, spray-on deposition,electrochemical plating or deposition, electroless plating,photo-resists, UV curing and/or densification, micro-machining usingprecision saws and/or other mechanical cutting/shaping tools, selectivemetallization and/or solder deposition, chemical-mechanical polishingfor planarizing, any other suitable spatially-selective materialprocessing techniques, combinations thereof, and/or functionalequivalents thereof. In particular, it should be noted that any stepinvolving “spatially-selectively providing” a layer or structure mayinvolve either or both of: spatially-selective deposition and/or growth,or substantially uniform deposition and/or growth (over a given area)followed by spatially-selective removal. Any spatially-selectivedeposition, removal, or other process may be a so-called direct-writeprocess, or may be a masked process. It should be noted that any “layer”referred to herein may comprise a substantially homogeneous materiallayer, or may comprise an inhomogeneous set of one or more materialsub-layers. Spatially-selective material processing techniques may beimplemented on a wafer scale for simultaneous fabrication/processing ofmultiple structures on a common substrate wafer.

It should be noted that various components, elements, structures, and/orlayers 11 described herein as “secured to”, “connected to”, “mountedon”, “deposited on”, “formed on”, “positioned on”, etc., a substrate maymake direct contact with the substrate material, or may make contactwith one or more layer(s) and/or other intermediate structure(s) alreadypresent on the substrate, and may therefore be indirectly “secured to”,etc, the substrate.

The phrase “operationally acceptable” appears herein describing levelsof various performance parameters of optical components and/or opticaldevices, such as optical power transfer efficiency (equivalently,optical coupling efficiency), optical loss, undesirable reflection, andso on. An operationally acceptable level may be determined by anyrelevant set or subset of applicable constraints and/or requirementsarising from the performance, fabrication, device yield, assembly,testing, availability, cost, supply, demand, and/or other factorssurrounding the manufacture, deployment, and/or use of a particularoptical component or assembly. Such “operationally acceptable” levels ofsuch parameters may therefor vary within a given class of devicesdepending on such constraints and/or requirements. For example, a loweroptical coupling efficiency may be an acceptable trade-off for achievinglower device fabrication costs in some instances, while higher opticalcoupling may be required in other instances in spite of higherfabrication costs. The “operationally acceptable” coupling efficiencytherefore varies between the instances. Many other examples of suchtrade-offs may be imagined. Optical components, planar waveguides, andfabrication and/or assembly methods therefor as disclosed herein, andequivalents thereof, may therefore be implemented within tolerances ofvarying precision depending on such “operationally acceptable”constraints and/or requirements. Phrases such as “substantiallyspatial-mode-matched”, “substantially index-matched”, “so as tosubstantially avoid undesirable reflection”, and so on as used hereinshall be construed in light of this notion of “operationally acceptable”performance.

While particular examples have been disclosed herein employing specificmaterials and/or material combinations and having particular dimensionsand configurations, it should be understood that many materials and/ormaterial combinations may be employed in any of a variety of dimensionsand/or configurations while remaining within the scope of inventiveconcepts disclosed and/or claimed herein. It should be pointed out thatwhile wafer-scale processing sequences are set forth as examples, any orall of the processing sequences set forth herein, and/or equivalentsthereof, may also be implemented for smaller sets of components, or forindividual components, while remaining within the scope of the presentdisclosure and/or appended claims. It is intended that equivalents ofthe disclosed exemplary embodiments and methods shall fall within thescope of the present disclosure and/or appended claims. It is intendedthat the disclosed exemplary embodiments and methods, and equivalentsthereof, may be modified while remaining within the scope of the presentdisclosure and/or appended claims.

For purposes of the present disclosure and appended claims, theconjunction “or” is to be construed inclusively (e.g., “a dog or a cat”would be interpreted as “a dog, or a cat, or both”; e.g., “a dog, a cat,or a mouse” would be interpreted as “a dog, or a cat, or a mouse, or anytwo, or all three”), unless: i) it is explicitly stated otherwise, e.g.,by use of “either . . . or”, “only one of . . . ”, or similar language;or ii) two or more of the listed alternatives are mutually exclusivewithin the particular context, in which case “or” would encompass onlythose combinations involving non-mutually-exclusive alternatives. Forpurposes of the present disclosure or appended claims, the words“comprising”, “including”, “having”, and variants thereof shall beconstrued as open ended terminology, with the same meaning as if thephrase “at least” were appended after each instance thereof.

1. A method comprising: propagating an optical signal in a first opticalwaveguide positioned on a waveguide substrate; transmitting the opticalsignal out of the first optical waveguide through an end face thereof;receiving, into a second optical waveguide positioned on the waveguidesubstrate and optically end-coupled with the first optical waveguide,through an end face of the second optical waveguide, at least a portionof the optical signal that is transmitted through the end face of thefirst optical waveguide, the received portion of the optical signalbeing reflected by or transmitted through an end wall of an opticalcomponent, the optical component comprising (i) a horizontal member,(ii) two side walls integrally formed with and protruding from thehorizontal member, (iii) the end wall integrally formed with andprotruding from the horizontal member, the end wall, side walls, andhorizontal member partially enclosing an interior volume, and (iv)optical functionality imparted on at least a portion of the end wall,wherein the two side walls are arranged for engaging the waveguidesubstrate so as to position the end wall at a desired angle with respectto the waveguide substrate and so that the waveguide substrate partiallyencloses the interior volume opposite the horizontal member, and theoptical component is mounted on the waveguide substrate with the twoside walls engaged therewith; and propagating in the second opticalwaveguide that portion of the optical signal received through the endface thereof.
 2. The method of claim 1 wherein the optical functionalityis imparted by: i) at least one optical coating formed on at least onesurface of the optical component end wall; ii) at least one curvedsurface of the optical component end wall; iii) at least one surface ofthe optical component layer with a spatially-varying surface profile;iv) at least one spatially-varying optical property of the opticalcomponent end wall; v) at least one anisotropic optical property of theoptical component end wall; or vi) at least one spectrally-varyingoptical property of the optical component end wall.
 3. The method ofclaim 1, wherein the first optical waveguide or the second opticalwaveguide comprises a planar optical waveguide formed on the waveguidesubstrate.
 4. The method of claim 1 wherein the optical component ismounted on the waveguide substrate with an alignment surface formed onthe horizontal member or on at least one of the side walls engaged withan alignment surface formed on the planar waveguide or the waveguidesubstrate.
 5. The method of claim 1 wherein the optical component ismounted on the waveguide substrate with an alignment mark formed on thehorizontal member or on at least one of the side walls aligned with analignment mark formed on the planar waveguide or the waveguidesubstrate.
 6. The method of claim 1 wherein optical functionality isimparted by at least one optical coating formed on at least one surfaceof the optical component end wall.
 7. The method of claim 6 wherein theoptical coating comprises a spectrally-selective filter coating.
 8. Themethod of claim 1 wherein that portion of the optical signal received bythe second optical waveguide is reflected by the optical component endwall, the method further comprising: receiving, into a third opticalwaveguide positioned on the waveguide substrate and opticallyend-coupled with the first optical waveguide, through an end face of thethird optical waveguide, a second portion of the optical signal that istransmitted through the end face of the first optical waveguide, thesecond received portion of the optical signal being transmitted throughthe optical component end wall; and propagating in the third opticalwaveguide that portion of the optical signal received through the endface thereof.
 9. The method of claim 8 further comprising: propagating asecond optical signal in a fourth optical waveguide positioned on thewaveguide substrate and optically end-coupled with the third opticalwaveguide; transmitting the second optical signal out of the fourthoptical waveguide through an end face thereof; receiving, into the thirdoptical waveguide through the end face thereof, at least a portion ofthe second optical signal that is transmitted through the end face ofthe fourth optical waveguide, the received portion of the second opticalsignal being reflected by the optical component end wall; andpropagating in the third optical waveguide that portion of the secondoptical signal received through the end face thereof.
 10. The method ofclaim 1 wherein that portion of the optical signal received by thesecond optical waveguide is reflected by the optical component end wall,the method further comprising: propagating a second optical signal in athird optical waveguide positioned on the waveguide substrate andoptically end-coupled with the second optical waveguide; transmittingthe second optical signal out of the third optical waveguide through anend face thereof; receiving, into the second optical waveguide throughthe end face thereof, at least a portion of the second optical signalthat is transmitted through the end face of the third optical waveguide,the received portion of the second optical signal being transmittedthrough the optical component end wall; and propagating in the secondoptical waveguide that portion of the second optical signal receivedthrough the end face thereof.
 11. The method of claim 1 wherein thatportion of the optical signal received by the second optical waveguideis reflected by the optical component end wall, the method furthercomprising: propagating a second optical signal in a third opticalwaveguide positioned on the waveguide substrate and opticallyend-coupled with the first optical waveguide; transmitting the secondoptical signal out of the third optical waveguide through an end facethereof; receiving, into the first optical waveguide through the endface thereof, at least a portion of the second optical signal that istransmitted through the end face of the third optical waveguide, thereceived portion of the second optical signal being transmitted throughthe optical component end wall; and propagating in the first opticalwaveguide that portion of the second optical signal received through theend face thereof.
 12. The method of claim 1 wherein that portion of theoptical signal received by the second optical waveguide is transmittedthrough the optical component end wall, the method further comprising:propagating a second optical signal in a third optical waveguidepositioned on the waveguide substrate and optically end-coupled with thefirst optical waveguide; transmitting the second optical signal out ofthe third optical waveguide through an end face thereof; receiving, intothe first optical waveguide through the end face thereof, at least aportion of the second optical signal that is transmitted through the endface of the third optical waveguide, the received portion of the secondoptical signal being reflected by the optical component end wall; andpropagating in the first optical waveguide that portion of the secondoptical signal received through the end face thereof.
 13. The method ofclaim 1 wherein one of the first or second optical waveguides comprisesa planar optical waveguide formed on the waveguide substrate and theother of the first or second optical waveguides comprises an opticalfiber mounted on the waveguide substrate and optically end-coupled towith the planar waveguide by transmission through the optical componentend wall.
 14. The method of claim 1 wherein the first optical waveguidecomprises a planar optical waveguide formed on the waveguide substrateand the second optical waveguide comprises a second planar opticalwaveguide formed on the waveguide substrate and optically end-coupled towith the planar waveguide by transmission through the optical componentend wall.
 15. The method of claim 1 wherein the first optical waveguidecomprises a first planar optical waveguide formed on the waveguidesubstrate and the second optical waveguide comprises a second planaroptical waveguide formed on the waveguide substrate and opticallyend-coupled to the first planar waveguide by reflection by the opticalcomponent end wall.
 16. The method of claim 15 wherein cores of thefirst and second planar waveguides are less than about 1 μm in height.17. The method of claim 15 wherein the first and second planarwaveguides form an angle between about 15° and about 35°.
 18. The methodof claim 1 wherein one of the first or second optical waveguidescomprises a first planar optical waveguide formed on the waveguidesubstrate and the other of the first or second optical waveguidescomprises a second planar optical waveguide formed on a second waveguidesubstrate and optically end-coupled to the first planar waveguide bymounting of the second planar waveguide on the first waveguidesubstrate.
 19. The method of claim 1 wherein one of the first or secondoptical waveguides comprises a planar optical waveguide formed on thewaveguide substrate and an end of the planar waveguide is receivedwithin the interior volume of the optical component.
 20. The method ofclaim 1 wherein the first or second optical waveguide comprises a planaroptical waveguide formed on the waveguide substrate and a substantiallytransparent embedding medium substantially fills an optical path betweenthe planar waveguide and the optical component end wall.
 21. The methodof claim 1 wherein: the optical component further comprises a secondsubstantially transparent end wall protruding from the horizontal memberand partially enclosing the interior volume opposite the first end wall,and optical functionality imparted on at least a portion of the secondend wall; the first or second optical waveguide comprises a planaroptical waveguide formed on the substrate; and the optical component ismounted on the waveguide substrate with a segment of the planar opticalwaveguide received within the interior volume and substantially enclosedby the optical component.
 22. The method of claim 1 wherein the opticalcomponent end wall is between about 20 μm and about 30 μm thick.
 23. Themethod of claim 1 wherein an end face of the first optical waveguide iswithin about 5 μm of a facing surface of the optical component end wall,and an end face of the second optical waveguide is within about 5 μm ofa facing surface of the optical component end wall.
 24. The method ofclaim 1 wherein at least one side wall is tilted and reflectively coatedso that light emerging from at least one of the optical waveguides andincident on the tilted side wall is redirected toward the waveguidesubstrate.
 25. A method comprising: propagating an input optical signalin a first planar optical waveguide formed on a waveguide substrate;propagating, in a second planar optical waveguide formed on thewaveguide substrate and optical end-coupled with the first planaroptical waveguide, an output optical signal received from a lasermounted on the waveguide substrate; transmitting the input opticalsignal out of the first optical waveguide through an end face thereof;transmitting the output optical signal out of the second opticalwaveguide through an end face thereof; receiving, into a third opticalwaveguide positioned on the waveguide substrate and opticallyend-coupled with the first optical waveguide, through an end face of thethird optical waveguide, at least a portion of the input optical signalthat is transmitted through the end face of the first optical waveguide,the received portion of the input optical signal being directed betweenthe first and third planar optical waveguides by an optical component,the optical component comprising (i) a horizontal member, (ii) two sidewalls integrally formed with and protruding from the horizontal member,(iii) an end wall integrally formed with and protruding from thehorizontal member, the end wall, side walls, and horizontal memberpartially enclosing an interior volume, and (iv) optical functionalityimparted on at least a portion of the end wall, wherein the two sidewalls are arranged for engaging the waveguide substrate so as toposition the end wall at a desired angle with respect to the waveguidesubstrate and so that the waveguide substrate partially encloses theinterior volume opposite the horizontal member, and the opticalcomponent is mounted on the waveguide substrate with the two side wallsengaged therewith; receiving, into the first optical waveguide throughthe end face thereof, at least a portion of the output optical signalthat is transmitted through the end face of the second planar opticalwaveguide, the received portion of the output optical signal beingdirected between the first and second planar optical waveguides by theoptical component; propagating in the third planar optical waveguide toa photodetector mounted on the waveguide substrate that portion of theinput optical signal received through the end face of the third planaroptical waveguide; and propagating in the first planar optical waveguidethat portion of the output optical signal received through the end facethereof.
 26. The method of claim 25 wherein the optical functionality isimparted on the end wall of the optical component by aspectrally-selective optical filter coating formed on at least onesurface of the end wall.
 27. The method of claim 25 wherein: the opticalfilter coating at least partly reflects the output optical signal and atleast partly transmits the input optical signal; the received portion ofthe output optical signal is directed between the first and secondplanar optical waveguides by reflection from the end wall of the opticalcomponent; and the received portion of the input optical signal isdirected between the first and third planar optical waveguides bytransmission through the end wall of the optical component.
 28. Themethod of claim 25 wherein: the optical filter coating at least partlytransmits the output optical signal and at least partly reflects theinput optical signal; the received portion of the output optical signalis directed between the first and second planar optical waveguides bytransmission through the end wall of the optical component; and thereceived portion of the input optical signal is directed between thefirst and third planar optical waveguides by reflection from the endwall of the optical component.
 29. The method of claim 25 furthercomprising: receiving the input optical signal to propagate in the firstplanar optical waveguide from an optical fiber optically end-coupled tothe first planar waveguide at a second end face thereof, the opticalfiber being mounted on the substrate in a fiber-alignment groove formedthereon; and transmitting at least a portion of the output opticalsignal from the second end face of the first planar optical waveguide topropagate in the optical fiber.
 30. The method of claim 25 wherein theoptical component is mounted with the end wall near the waveguide endfaces and with at least one of the waveguide end faces received withinthe interior volume.